The House Assassinations Committee suddenly began investigating itself yesterday in the face of accusations that an undercover agent it recruited had spied on Jerry Ray, filched his letters and secretly tape-recorded his conversations.

Ray is a brother of James Earl Ray, convicted killer of the Rev. Martin Luther King Jr.

According to a statement by the undercover agent, a former FBI informer named Oliver patterson of Blackjack, Mo., one committee investigator even assigned him to "secure samples of Jerry Ray's hair."

The charges prompted an abrupt withholding of additional funds for the committee's inquiries and sent it into a turmoil less than a week before the start of public hearings into King's murder in 1968.

The turnabout, which included a bit of gamesmanship at the expenses of The New York Times, was engineered by the controversial Mark Lane. Now the lawyer for king's convicted assassin, Lane led the lobbying effort to create the committee two years ago, but has since turned against it.

The committee's chief counsel, G. Robert Blakey, acknowledged that the allegations were "very serious" and said they would be thoroughly examined. But he refused further comment and declined even to say whether the committee had any undercover agents.

"I'm not authorized" to say. Blakey protested in a somewhat tense exchange with reporters yesterday morning, moments after a House Administration subcommittee had shelved the committee's report for $790,000 to carry it through the end of the year.

Rep. Samuel L. Devine (Ohio), the ranking Republican on both the Assassinations Committee and the subcommittee that funds it, complained that the inquiry would run out of money by Sept. 15 right in the middle of public hearings on President kennedy's assassination, without a fresh transfusion, but his colleagues were unimpressed. Subcommittee Chairman John H. Dent (D-Pa.) said the Assassinations Committee had $822,000 as of July 1, more than enough to keep it going until the current furor is settled and the Kennedy hearings completed.

The charges of comittee-authorized spying on Jerry Ray were first aired Monday in a St. Louis "news conference" that Lane had carefully orchestrated last weekend after enlisting Patterson as a defector willing to tell all. In a typewritten statement, the self-described undercover agent said he had "recruited" by committee investigator Conrad (Pete) Baetz early this year and sent to Georgia to "renew my relationship" with Jerry Ray.

According to Patterson, he had been an informer for the FBI on the activities of Jerry Ray and white supremacist J. B. Stoner from 1971 to 1974. Apparently the FBI supplied Patterson's name to the Assassinations Committee as a potential asset.

In any case, Patterson said in his statement that Baetz, a $24,000-a-year committee investigator based in St. Louis, "regularly instructed me to telephone Jerry Ray and to tape-record those conversations."

"I often did that while Baetz was in my house," continued patterson, an electronics salesman who used to operate a shop called Blackjack Radio out of his home. "Often Baetz would listen into the conversation by using earphones designed to monitor conversations. This went on for several months. Baetz took the tapes of the recorded conversations with him and gave me back tapes regularly."

Under rules adopted by the committee last year in the midst of another controversy, "no conversation of committee members or staff with any person shall be recorded without the prior knowledge and/or written consent of the person whose conversation is to be recorded." In addition, the rules state, "there shall be no electronic surveillance or wiretapping of any person."

A Madison County, III, deputy sheriff on leave for 3 year. Baetz was reportedly closeted here with committee officials yesterday. A representative of the committee quoted him as saying "I can't make any comment. I don't want to make any comment."

Patterson also said that on one occasion while he was in Washington with Jerry Ray - apparently in mid-April when both testified before the Assassinations Committee and shared a motel room during the trip - he searched Ray's belongings. Patterson said he found some letters from James Earl Ray to his brother along with a map "which Jerry had placed in his toilet articles bag."

"I took them, photocopied them, and sent the copies to Baetz," Patterson said.

He said Baetz later told him the documents were considered "so important" that they were discussed at a meeting in Washington attended by Blakey, "the director of the FBI and Attorney General [Griffin] Bell."

Asked about that, Blakey parried by asking whether he was really being asked to comment about such a "ridiculous' claim. Told that he was being asked just that, he declined to comment. He also refused to say whether he thought the committee itself. rather than some other body, ought to be conducting the investigation of Patterson's allegations. Finally Blakey demanded that all his "no comments" not be attributed to him by name.

According to Patterson, Baetz also sent him to Georgia to see Jerry Ray and "to secure samples of Jerry Ray's hair. A woman named Donna, who traveled with me at the time, assisted in securing hair samples."